3d from images
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The document provides an overview of techniques for generating 3D models from images, including assisted modeling using tools like SketchUp, photogrammetry using tools like ImageModeler and PhotoModeler, and multi-view stereo matching using tools like the Photosynth Toolkit, SfM Toolkit, Python Photogrammetry Toolbox, and Autodesk 123Dcatch. It discusses the underlying principles, calibration processes, dense matching techniques, and final model creation steps involved. The document recommends several free and commercial software tools and provides additional online resources for learning more about these 3D reconstruction methods.
3d from images
- 1. 03/10/2013 1 3D from images, an overview 9th October 2013 0 Perspective and Stereo We do perceive the environment three- dimensionality thanks to our stereo vision AND the perspective projection that occurs in our eyes.. Using the geometric laws of this two phenomena we can build the 3D geometry of the scene
- 2. 03/10/2013 2 Perspective Camera All starts here... a camera is defined by parameters: - Position - Orientation - Focal Length - Viewport Distortion Given a point in 3D space, it is know the projected point on photo plane Given a point in the photo, it is possible to trace back the ray which originated the pixel 2 paths... Two possible directions - Assisted Modeling - Automatic Stereo Matching The underlying principles are the same... but they sprouted different kind of tools... I'll cover the first, Matteo will take over later on As usual, this distinction is becoming blurry... ...things does converge, after all
- 4. 03/10/2013 4 Sketchup A very strange modeling tool. Follows more the way a technical drawing is done on paper (reporting/referencing) than the usual 3D modeling metaphore. Easier for people with a technical drawing/sketching background. Easier for people with no experience in 3D modeling. Focused towards modeling of buildings and mechanical entities... Acquired by Google some years ago... distributed now as a semi-free tool http://sketchup.google.com/ Sketchup – the Luni Temple An ideal tool for very regular buildings... like this one (regular does not equal new) http://sketchup.google.com/
- 5. 03/10/2013 5 Sketchup Photo Match Assited modeling from a SINGLE photo Calibration: axis and vanishing points markup Modeling: 3D drawing by axis/reference reporting Partial calibration, with only a single photo, only the axis can be recovered. SketchUp can be used to model by reporting/referencing Example 1 – Example 2 Photogrammetry Perspective & stereo Common reference points are marked on multiple images… From these correspondences it is possible to calculate camera position/parameters and 3D location of the marked points
- 6. 03/10/2013 6 ImageModeler Photogrammetry commercial tool Points are marked on input images, camera are fully calibrated using these points, camera are calibrated and modeling can be done using the recovered 3D points Acquired by Autodesk... now it costs three times the old price (with the same features) PhotoModeler Photogrammetry commercial tool The tool for the professionals... Two steps: camera calibration (with markers and references) and camera pose estimation. Modeling and measuring with lots of different tools Very, very, very complex to use...
- 7. 03/10/2013 7 MULTI-VIEW STEREO MATCHING 1 - Automatic matching of images The entire process is based on finding matches between images. Record your pictures not too far apart, so the computer can match them easily!
- 8. 03/10/2013 8 2 - Camera Calibration No prior knowledge about camera calibration is available, so all information must be recovered from the images It is therefore important that enough information is present in the images! Important factors: Motion of the camera General structure of the scene Enough overlap (only points that are visible in at least 3 images are useful) What you want reconstruct and how you get the photos have great influence on the final reconstruction (!!) Calibrated Cameras: what you can do with them Photo Tourism Having a set of (even etherogeneous) images, you can navigate the photo collection in a “spatially coherent” way. It evolved into PhotoSynth (see later).
- 9. 03/10/2013 9 3 - Dense Matching After recovery of the camera calibration, dense depth maps are computed These contain the depth of every pixel and a quality measure (how confident we are of each particular pixel) Depth Map Photosynth Toolkit The Photosynth toolkit is the result of the work of people from a Blog (Visual Experiments) The code of Bundler (SIFT+Camera Calibration) has been made available recently In alternative, it’s possible to use the Photosynth service Moreover, further code for the surface reconstruction (CMVS -> PMVS) The Toolkit is available and works locally
- 10. 03/10/2013 10 Photosynth Toolkit Also the Photosynth toolkit can be integrated with MeshLab, so that the final result can be improved! SfMToolkit It’s the same toolkit as PhotosynthToolkit, but it’s completely local http://www.visual- experiments.com/demos/sfmtoolkit/ Good: completely local, no upload, control on parameters Bad: completely local, sometimes it crashes…
- 11. 03/10/2013 11 Python Photogrammetry Toolbox Developed by Arc-Team, open source and free, for Debian and Win (32 and 64bit) http://www.arc-team.com/ Good: completely local, interface, control on parameters, video tutorial Bad: completely local, a bit tricky to install… Autodesk 123Dcatch Very well engineered tool... Works on a remote server, like Arc3D Produces a complete, textured model http://www.123dapp.com/catch It is free (for now), and works very very well. It is fast, works on difficult datasets and the results looks good. However, not really high resolution, and there is less control over the process. It is a good tool to start with...
- 12. 03/10/2013 12 Autodesk 123Dcatch 3 PhotoScan Commercial, low cost tool: 59 € for educational license, 179€ standard license. (win, mac & linux) Fast, work on local machine, directly produce textured model. Very robust and reliable... We have used it with good results on many diverse datasets. They also have a free tool to process images taken with stereo (two lenses) cameras....
- 13. 03/10/2013 13 PhotoModeler - dense Photogrammetry commercial tool, 2nd version The tool is the same as before... after doing the camera calibration, instead of using only user-picked points, the system does a dense- matching. The result is quite similar to a range map... you need to do standard processing in order to obtain a 3D model... Model creation with MeshLab After the 3D model is exported in MeshLab, there’s a procedure to enhance it a bit and have a final result: Cleaning Sampling Poisson reconstruction Poisson Model cleaning Vertex Color Transfer Cleaning Scaling Saving!
- 14. 03/10/2013 14 Conclusion The methods for the acquisition of 3D content from images have become an interesting alternative to 3D scanning. Probably they won’t take the place of 3D Scanning, but they could be a valid solution in a number of practical and professional applications. Nowadays, they are already used in archeologists everyday work, and they are undergoing a sort of standardization process. Knowing these yechnologies is key to be able to deal with 3D and CH. Wanna know more? Check the webpage of my University course: http://vcg.isti.cnr.it/~dellepiane/Corso.html (page in italian, slides mostly in English) You’ll find slides, datasets, links etc etc Do you want to learn how to use MeshLab? Start from Mister P. Video tutorials http://www.youtube.com/user/MrPMeshLabTutorials Several playlists available